Added code for a pause command for a container process.

Like runc, the pause command will pause the processes of the given container.
It will set that container's status to "paused."
A resume command will be be added to unpause and continue running the process.

PiperOrigin-RevId: 200789624
Change-Id: I72a5d7813d90ecfc4d01cc252d6018855016b1ea

3 files changed, 64 insertions, 7 deletions

diff --git a/runsc/container/container.go b/runsc/container/container.go
index 40c31ca7f..dc7fccdee 100644
--- a/runsc/container/container.go
+++ b/runsc/container/container.go
@@ -316,7 +316,7 @@ func (c *Container) Event() (*boot.Event, error) {
 // Pid returns the Pid of the sandbox the container is running in, or -1 if the
 // container is not running.
 func (c *Container) Pid() int {
-	if c.Status != Running && c.Status != Created {
+	if c.Status != Running && c.Status != Created && c.Status != Paused {
 		return -1
 	}
 	return c.Sandbox.Pid
@@ -349,6 +349,23 @@ func (c *Container) Checkpoint(f *os.File) error {
 	return c.Sandbox.Checkpoint(c.ID, f)
 }
 
+// Pause suspends the container and its kernel.
+// The call only succeeds if the container's status is created or running.
+func (c *Container) Pause() error {
+	log.Debugf("Pausing container %q", c.ID)
+	switch c.Status {
+	case Created, Running:
+		if err := c.Sandbox.Pause(c.ID); err != nil {
+			return fmt.Errorf("error pausing container: %v", err)
+		}
+		c.Status = Paused
+		return c.save()
+	default:
+		log.Warningf("container %q not created or running, not pausing", c.ID)
+		return nil
+	}
+}
+
 // State returns the metadata of the container.
 func (c *Container) State() specs.State {
 	return specs.State{
diff --git a/runsc/container/container_test.go b/runsc/container/container_test.go
index b6d19bf33..5659abab3 100644
--- a/runsc/container/container_test.go
+++ b/runsc/container/container_test.go
@@ -459,6 +459,40 @@ func TestCheckpoint(t *testing.T) {
 	}
 }
 
+// TestPause tests that calling pause successfully pauses the container.
+// It checks that no errors are returned and that the state of the container
+// is in fact 'Paused.'
+func TestPause(t *testing.T) {
+	spec := testutil.NewSpecWithArgs("sleep", "100")
+
+	rootDir, bundleDir, conf, err := testutil.SetupContainer(spec)
+	if err != nil {
+		t.Fatalf("error setting up container: %v", err)
+	}
+	defer os.RemoveAll(rootDir)
+	defer os.RemoveAll(bundleDir)
+
+	// Create and start the container.
+	cont, err := container.Create(testutil.UniqueContainerID(), spec, conf, bundleDir, "", "")
+	if err != nil {
+		t.Fatalf("error creating container: %v", err)
+	}
+	defer cont.Destroy()
+	if err := cont.Start(conf); err != nil {
+		t.Fatalf("error starting container: %v", err)
+	}
+
+	// Pause the running container.
+	if err := cont.Pause(); err != nil {
+		t.Errorf("error pausing container: %v", err)
+	}
+
+	// Confirm the status of the container is paused.
+	if got, want := cont.Status, container.Paused; got != want {
+		t.Errorf("container status got %v, want %v", got, want)
+	}
+}
+
 // TestCapabilities verifies that:
 // - Running exec as non-root UID and GID will result in an error (because the
 //   executable file can't be read).
diff --git a/runsc/container/status.go b/runsc/container/status.go
index 8da1b4e89..bf177e78a 100644
--- a/runsc/container/status.go
+++ b/runsc/container/status.go
@@ -19,13 +19,17 @@ package container
 type Status int
 
 const (
-	// Creating indicates "the container is being created".
-	Creating Status = iota
-
 	// Created indicates "the runtime has finished the create operation and
 	// the container process has neither exited nor executed the
 	// user-specified program".
-	Created
+	Created Status = iota
+
+	// Creating indicates "the container is being created".
+	Creating
+
+	// Paused indicates that the process within the container has been
+	// suspended.
+	Paused
 
 	// Running indicates "the container process has executed the
 	// user-specified program but has not exited".
@@ -39,10 +43,12 @@ const (
 // CLI spec and should not be changed.
 func (s Status) String() string {
 	switch s {
-	case Creating:
-		return "creating"
 	case Created:
 		return "created"
+	case Creating:
+		return "creating"
+	case Paused:
+		return "paused"
 	case Running:
 		return "running"
 	case Stopped: